In an excavation site of a mine, a work vehicle such as a dump truck and an excavator is operated. The work vehicle used in a mine has a big size. Due to this, surroundings monitoring system has been proposed, which monitors surroundings of a work vehicle using a detection device capable of detecting an object around the work vehicle so that an operator can easily recognize the situation of the surroundings with the aid of side mirrors or the like. An example of a surroundings monitoring apparatus which uses a camera is disclosed in Patent Literature 1.